1. Field of the invention
The present invention relates to 4.sup.G -alpha-D-glucopyranosyl rutin shown by the formula [I]: ##STR1## and its preparation and uses.
2. Description of the Prior Art
Rutin, which has a chemical structure shown with the formula [II]: ##STR2## has been known as a yellow pigment and vitamin P with physiological activities such as stabilization of blood vessel, prevention of hemorrhage and regulation of blood pressure, and has been used from ancient times in foodstuffs, pharmaceuticals and cosmetics.
It is known that vitamin P takes part in some physiological activities of vitamin C in vivo; for example, in the hydroxylation of proline and lysine which are necessary to synthesize collagen as the main element of living connective tissues; the oxidation-reduction reaction of cytochrome C wherein Fe.sup.+++ is reduced to Fe.sup.++ ; and in the immunopotentiation via the increase of leukocyte. These are because vitamin P plays a significant role in the maintenance and promotion of health in living bodies.
Nowadays the use of rutin is not limited to agents which enrich vitamin P as a nutritive element, but is extending in various applications. More particularly, because of the chemical structure and physiological activities, rutin is useful as a yellow coloring agent and antioxidant alone or in combination with one or more vitamins, for example, in foods, beverages and pharmaceuticals for susceptive diseases such as a preventive and remedy for circulatory diseases, as well as a yellow coloring agent and uv-absorbent in cosmetics such as skin-refining and skin-whitening agents.
Rutin is, however, hardly soluble in water (only about 1 g in 8 liters of water or about 0.01 w/v % at ambient temperature). This renders its practical use very difficult.
To improve this low water-solubility, some methods have been attempted. For example, Japanese Patent Publication No. 1,677/50 disclose a method wherein aliphatic compounds with amino groups are added to rutin for its increased water-solubility; Japanese Patent Publication No. 2,724/51, another method wherein monohalogeno acetic acids are allowed to act on rutin to convert it into sodium monohalogeno acetates having an increased water-solubility; and Japanese Patent Publication No. 1,285/54, one another method wherein "Rongalit", a commercialized sodium hydroxymethane, is allowed to act on rutin to convert it into sulfite compounds having an increased water-solubility.
These methods have, however, the drawback that the use of amino compounds, monohalogeno acetic acids and sulfite compounds may result in an undesirable physiological activity and/or toxicity in final products, as well as rendering their purification very difficult.
We proposed a much safer solubilization method in Japanese Patent Publication No. 32,073/79, wherein a biosynthesis by saccharide-transferring enzyme is utilized to transfer equimolar or more glucose residues from a partial starch hydrolysate to rutin to form alpha-glycosyl rutin having an improved water-solubility.
Japanese Patent Publication No. 32,073/79 describes the conversion of rutin into a mixture of rutin glycosides wherein equimolar or more glucose residues are bound for an improved water-solubility, but does not characterize particular glycosides.
This is obvious from Table in page 3 of the Japanese Patent Publication, which describes that the designation of glycosides is based on the speculation, and the position to which glucose residues are newly transferred has not been clarified.
To extend the application of alpha-glycosyl rutin, characterization of glycosides has been in long expectation. Realization of novel glycosides with a clarified chemical structure has been in strong demand.